Poonam Uniyal

Effect of dysprosium doping on structural, dielectric and ferroelectric properties of PLZT (65/35) ceramics

Dy modified polycrystalline PLZT (65/35) i.e. Pb0.92-xLa0.08Dyx(Zr0.65Ti0.35)1-x/4O3 materials were synthesized by solid state reaction technique. X-ray pattern of compounds confirmed the formation of single rhombohedral phase. Detailed dielectric studies of the compounds as a function of temperature shows that broadening of permittivity peak and transition temperature depends on Dy3+ ions concentration. Analysis of Diffuseness (□) of the broadened dielectric peaks of materials gave its value between 1 & 2, indicating the different degree of substitutional disorder in the system. The transition temperature (Tc) was found to shift towards lower temperature by 40°C with Dy concentration. The P-E loop measurement at room temperature confirms the ferroelectric behavior.

Calcination temperature influenced multiferroic properties of Ca-doped BiFeO3 nanoparticles

The influence of Ca-doping and particle size on structural, morphological and magnetic properties of BiFeO3 nanoparticles has been studied. A sol-gel method was employed for the synthesis of nanoparticles and their particle size was tailored by varying the calcination temperature. Structural analysis revealed a rhombohedral distortion induced by Ca-substitution. The broadening of diffraction peaks with decreasing calcination temperature was indicative of reduction in crystallite size. The morphological analysis revealed the formation of agglomerated nanoparticles having average particle size ranging from 10-15 and 50-55 nm for C4 and C6, respectively. The agglomeration is attributed to high surface energy of nanoparticles. Ferromagnetism has been displayed by all the synthesized nanoparticles. Enhancement of saturation magnetization with Ca-substitution is attributed to suppression of spin cycloid structure by the reduction in size, lattice distortion and creation of oxygen vacancies by the substitution o...

Study of phase transformation and microstructure of alcohol washed titania nanoparticles for thermal stability

Nanostructured titania have been successfully synthesized by hydrolysis of alkoxide at calcination temperatures 500 °C, 600 °C and 700 °C. As the calcination temperature increases, alcohol washed samples show lesser rutile content as compared to water washed samples. Morphology and Particle sizes was determined by field emission scanning electron microscopy (FESEM), while thermogravimetric-differential scanning calorimetry (TG-DSC) was used to determine thermal stability. Alcohol washed samples undergo 30% weight loss whereas 16% in water washed samples was observed. The mean particle sizes were found to be increase from 37 nm to 100.9 nm and 35.3 nm to 55.2 nm for water and alcohol washed samples respectively. Hydrolysis of alkoxide was shown to be an effective means to prepare thermally stable titania by using alcohol washed samples as a precursor.

Synthesis and characterization of BiFeO3 for photocatalytic degradation of azo dye

A novel approach is reported to synthesize single phase BiFeO3 via. sol-gel auto combustion method using glycine as fuel. Synthesized powder was subjected to annealing at different temperatures, i.e. 400 °C, 450 °C, 500 °C, 550 °C, and 600°C. Crystal structure of BiFeO3 samples examined by X-ray diffraction indicates that the samples were single-phased with different particle sizes, as particle sizes are temperature dependent and crystallized in rhombohedral structure. As the temperature was increased, the diffraction peak intensity of BiFeO3 in the XRD spectra gradually enhanced and the diffraction peaks became sharper. The optical properties of the resultant BiFeO3 were characterized using UV-Vis spectrophotometer over the range of 350-800 nm. UV-vis spectra of all the samples indicate that optical band gap lies in the visible region in the range of 2.2-2.07 eV at all temperatures. Moreover, photocatalytic properties of the BiFeO3 powders were investigated by the photodegradation of Reactive Black-5 (RB-5).